Question

1457 (2.2x10^-8) follow up question: Identify the following as acidic, basic or neutral: pH = 4.56 pH = 10.4 [OH-] = 2.4x10-8 Reply Quote Select: All None Message Actions Expand All

Answer 1

(a) pH = 4.56 is acidic

(b) pH = 10.4 is basic

(c) [OH-] = 2.4x10-8, thus
`pH = -Log (4.16x10^(-7)) = 6.3` is acidic

Step-by-step explanation:

The pH is the mesure of the acidity or bacisity of a solution. It indicates the concentration of protons in a solution and it is define as:

`pH = -Log ([H^(+)])`

The scale of pH goes from 1 to 14, being 1 the most acid condition and 14 de most basic condition. Also a pH = 7 is a neutral condition.

Therefore, if the pH is: 1 ≤ pH < 7 the solution will be acidic and if the pH is 7 < pH ≤ 14 the solution will be basic.

To answer (c) it is also necessary to consider the water autoionization to calculate the protons concentration as shown bellow

`K_(w) =[H^(+) ][OH^(-)]=10^(-14)`

`[H^(+) ]=(10^(-14))/([OH^(-)])`

For (c) [OH-] = 2.4x10-8

`[H^(+) ]=(10^(-14))/(2.4x10^(-8))=4.16x10^(-7)`

And using the definition of pH

`pH = -Log (4.16x10^(-7)) = 6.3`